Following peripheral nerve injury in humans, fascicular reanastomosis is one method of promoting reinnervation and the return of useable function to the denervated tissues. The major factor limiting the success of this procedure has been the ability to match appropriate fascicles in the proximal and distal nerve stumps. The constancy of regional anatomical fascicular patterns, elegantly documented by Sunderland, is utilized by nerve surgeons to match fascicles (1). However, dramatic coalescence and redistribution of fascicles within a few milimeters of nerve length militates against fascicular reunion (1). Electrical stimulation testing of individual fascicles demonstrates motor and sensory responses, but the complement of sensory and motor axons in these fascicles in unknown (2). Another alternative, histochemical acetylcholinesterase staining of nerve stump biopsies distinguishes highly reactive motor axons from less reactive sensory fibers. However, the 24 to 36 hours of incubation time required for human nerves necessitates a two-stage nerve repair on separate days (3,4). At present, anatomical patterns remain the primary guides for fascicular reanastomosis.
Recently, Riley et al, discovered that carbonic anhydrase (CA) histochemistry distinguishes dorsal sensory root axons from ventral motor root axons in the rat (5,6). The presence of CA activity in sensory neurons was corroborated immunocytochemically (7).
It has been recently discovered that human peripheral nerves exhibit differential carbonic anhydrase activity and staining properties which allow for the discrimination between nerve fascicles (8, 9). The staining reaction required only 3 to 4 hours. As a result, histochemically-aided nerve repair can be accomplished in a single operation.
Nerve fascicles of human peripheral nerves can be distinguished histochemically from one another in nerve biopsies by the carbonic anhydrase staining patterns of their constituent myelinated axons (8,9). To use the staining procedure clinically would require transporting nerve biopsies from the surgery room to a histochemical laboratory for sectioning and reacting the specimens, drawing maps of the fascicular staining patterns and returning the diagrams to the surgeon for use in matching fascicles in the proximal and distal nerve stumps.